In the medical field, it is critical that a supply of various blood products, such as platelets, plasma, and so forth, be readily available. Such products are preferably stored for immediate use, generally in flexible bags which can be easily attached to the appropriate tubes and lines for use by the patient.
Often, however, blood products are often stored for periods of time before use. During those storage periods, environmental factors, such as changes in temperature, may cause the quality of the blood product to be affected, making use of the blood product questionable or inadvisable. For instance, if the pH level of the blood product drops below a certain level, the blood product quality is compromised. Likewise, if bacteria have entered the storage container and contaminated the blood product, a decrease in glucose levels may be detected, indicating that the blood product is no longer of a useable quality.
Such changes in the quality of the blood product are generally undetectable by visual inspection. Instead, a sample of the blood product may have to be removed from the storage container and tested for assurance that the quality of the product is satisfactory.
Various devices have been created to address the problems associated with monitoring the quality of stored blood products. For example, the apparatus described in U.S. Pat. Nos. 4,952,498 and 5,051,360, both to Waters, are adapted to detect gas-generating activity of microorganisms in a storage vessel. A portion of the vessel inflates to indicate existence of an increase in pressure within the vessel, caused by microorganism activity, which is detectable by visual monitoring.
U.S. Pat. No. 5,514,106 to D{character pullout}Silva discloses a storage bag having means for indicating the status of the contents of the bag, specifically, whether the contents have been subjected to a treatment process, such as illumination or radiation sterilization. overlapping portions of the bag form a flap having at least one hole punched therethrough which is capable of detection by a sensor to indicate treatment of the fluid within the bag. The bag may included a polarizing piece.
Likewise, the devices shown in WO 92/19284 and JP406007410 each disclose blood storage bags having indicia that visibly change when irradiated to indicate that the contents have been exposed to radiation.
U.S. Pat. No. to Malcolm et al discloses a testing and dispensing apparatus for measurement of the pH level of the contents contained in a storage vessel, comprising a dispensing tube and standard pH indicator removably received within the tube.
U.S. Pat. Nos. 2,856,885 and 2,856,930 to Huyck et al each disclose temperature indicators for blood storage containers which specifically indicate whether the contents of a blood storage container have reached a temperature exceeding 50.degree. F. The devices utilize a tube filled with a selected indicator liquid.
In a seemingly unrelated technical area, known as separation technology, plugged pore membranes have been employed with storage containers, specifically to preserve and maintain the contents stored therein. Generally, a plugged pore membrane is used to separate two substances, and consists of a membrane having a number of small and larger pores plugged with selected polymers. The polymers are erodible upon exposure to certain environmental conditions. Erosion of the polymer allows one of the substances to pass through the membrane, depending on the size of the pores from which the polymer was eroded, thereby treating the second substance and preventing spoilage and promoting preservation.
As U.S. Pat. No. 5,261,870 to Hammerstedt et al discloses, suitable applications include cell cultures and cryobiology, preingestion preservation and storage of food and pharmaceuticals, shelf-life extension of polymers, proteins and other products, and the containing, transporting and dispensing of active agents, including cells, herbicides, pesticides, fertilizers, and cell growth nutrients or other biologically active agents for use in laboratory or industrial settings. The Hammerstedt separation barrier is specifically contemplated for the preservation of rooster and turkey sperm for use in commercial artificial insemination applications.
Erodible polymers and microspheres have been employed in the pharmaceutical industry, specifically, in dissolvable capsules and even silicon rubber compounds, from which a drug is slowly released and administered to a patient over periods of hours or days as the polymer is dissolved by exposure to certain substances or environmental factors.
None of the above described art, however, has addressed the problem of conveniently monitoring and sustaining the quality of stored blood products by incorporating a responsive, microporous membrane into a blood storage container. Accordingly, a need exists for a blood storage bag adapted to detect and indicate changes in selected characteristics of blood products, such as pH, and for a storage bag which also may initiate the addition of buffers and nutrients to the product when needed to sustain or improve the quality of the product, preventing spoilage and waste.